Direct visual observation alone is often inadequate for identification of abnormalities in a specimen being examined, whether the specimen is a biological specimen or otherwise. Observation of many medical conditions in biological specimens of all kinds is well known. It is common in medical examination to perform visual examinations in disease diagnosis. For example, visual examination of the cervix can discern areas where there is a “suspicion” of pathology. In some instances, filters can be used to improve visual differentiation of normal and abnormal tissues. In other situations, when tissues of the cervix are examined in vivo, chemical agents such as acetic acid can be applied to enhance the differences in appearance between normal and pathological areas. These techniques form an integral part of a colposcopic examination of the cervix. Colposcopists may amplify the difference between normal and cancerous tissue with the application of various “activation” agents, the most common being acetic acid, at approximately 3% to 5% concentration, or an iodine solution, such as Lugol's iodine or Shiller's iodine. Even when the cervical tissues are viewed through a colposcope by an experienced practitioner with the application of acetic acid, correct diagnosis can be affected by subjective analysis. A variety of methods using optical techniques have been directed towards the diagnosis of cancer and other pathologies, particularly involving the cervix. Certain of these systems and methods have limitations that render them unsuitable for use as screening procedures.
While there have been extensive developments in the field of cancer diagnosis, none of these are well adapted for screening large populations. Currently, disease diagnoses are made predominately from pathological examinations of biopsied tissue. Techniques such as biopsies, while being the definitive determination of the presence of disease, are labor-intensive and operator-dependent, thus unsuitable for screening large populations. As another example, medical imaging techniques, depending on their cost, resource requirements and patient accessibility, may be unsuitable for population screening.
To be well accepted in the medical community, a screening method should be sufficiently sensitive and specific to identify abnormalities accurately. Furthermore, a screening method ideally is easy to perform so that it can be carried out rapidly on an otherwise healthy patient. In addition, to be cost effective the screening method should not require the use of expensive resources, including a significant time commitment from costly, highly trained medical personnel. Generally, screening settings advantageously employ less skilled operators and more operator-independent technology.